Tone control device



Aug.26,1941. A SCI-{ONE ETAL "2,254,122

TONE CONTROL DEVICE Filed July 51, 1957 INVE NTOR ALFRED SO /ONE AND 4. 06% STEFFENS BY A " ATTORNEY Patented Aug. 26, 1941 UNITED STATES TONE CONTROL DEVICE corporation of Germany Application July 31, 1937, Serial No. 156,628

In Germany August 10, 1936 3 Claims.

It has been proposed in wireless receiving apparatus, more especially in radio receivers to provide arrangements for the simultaneous or almost simultaneous control of the bandwidth in the high-frequency part and of the timbre or tone, i.' e. the frequency band in 'the audiofrequency part. The disadvantage hereby is that at a high selectivity in the band of powerful transmitters such far reaching tone control already takes place through narrowing of the frequency band in the high-frequency part, that an additional tone control in the audio-frequency range is not required, causing at the most a distortion'of the timbre.

Obviously, a separate control means may be provided in the high-frequency part and in the audio-frequency part, but this complicates the handling of the receiver in an unnecessary manner.

Contrary thereto, the invention furnishes a more suitable solution and in receivers with arrangements for controlling the band width in the high-frequency part and for varying the frequency characteristic in the audio-frequency part, the invention resides in that the control arrangements are so adapted and movably arranged that both types of control can be carried out in succession with a single setting oran.

In this way the possibility is given of carrying out in common both types of control only when necessary, so that if hereby for instance the variation in the tone obtained by the control of the band width is not sufiicient, the tone con:- trol following the first type of control is continued in the audio-frequency part. This measure affords the advantage that if tone control is required, owing, tothe use of the band width control for varying the tone, the selectivity will be increased simultaneously which is at any rate an advantagein -receiving the transmitters with sufficiently sharp. separation. Only if the allowable degree of selectivity is not reached determined for instance by the coupling degree of the coil arrangement used, will the tone control be continued in the audio-frequency part.

In special cases in which a high selectivity is of no importance or the existing selectivity sufficient, the types of control can be in the reversed sequence, so that at first the frequency characteristic is changed in the audio-frequency part, and thereupon the band width in the highfrequency part. At any rate it is essential to the proposal according to the invention, that the two types of control support each other, and that they follow in succession.

The invention will be elucidated in the following on hand of an example of construction represented in the Figures 1 to 3.

In Figure 1 there is shown at first a circuit diagramof a wireless receiving apparatus containing .eV band filter l in the high-frequency part. The filter consists in the ordinary way of condensers 2 and a fixedly set coupling coil pair .3 and coupling coils 4 and 5 relatively movable to each other. The band width can be controlled byv moving these coils such as indicated by the arrow 6.

For controlling the tone or frequency characteristic in the audio frequency part the condenser resistor combination 8/9 placed in the grid circuit of the output tube 1 is provided. The resistor 9 is variable, and causes the variation of the frequency characteristic. As already mentioned, there exists between the operation of the two control arrangements a relationship indicated by the dotted line H such that at first the coupling arrangement 1/5 is operated for corrtrolling the tone, and only therement of the coupling arrangement 4/5 no appreciable change in resistance takesplaoe but only when the said displacement has come to an end.

The characteristic of the resistance can best be seen from Figure 2 in which it is designated by W. The use of a turnable resistor with a range of displacement of 270 is considered, whose resistance value is'plotted on the ordinate of the coordinate system shown, and does not substantially change within a displacement range of the current take oil of about 135. This range is designated by B and covers the range of effectiveness of the band width control arrangement. Only when the resistance moves over the other range F covering 135 does the control of the frequency characteristic in the audio-frequency part take place as far as this is necessary.

The mechanical set up of the arrangement is shown in Figure 3. In part the same reference characters are used as in Figure 1. Of the coils of the coupling arrangement 4/5 one, for instance that designated by 4 is mounted on a turning arm I l pressing by means of a spring l2 against the cam l4 arranged on the shaft I3 of the displacement arrangement. The cam engages the arm ll only in a certain displacement range of the turning shaft l3, and produces a change in the coupling degree between the coils 4 and 5. Thus in this range the band width will be controlled. In the other displacement range of the turning shaft I3 there prevails a constant loose coupling and the resistor 9 serving for varying the frequency characteristic in the audio frequency part will be decreased by means of a gliding contact and cord drive 16 tensioned by a spring II. During the engagement of the cam l4 with the arm I l the gliding contact of the resistor 9 is'likewise operated, but the change in resistance is but slight according to the range B in Figure 2. The range designated by F corresponds to the displacement range of the turning shaft l3 in which the cam I4 is not in engagement with the arm I l.

The arrangement is such that the two types of control support each other in succession, and

in such manner that a decrease in the band width in the high-frequency part is produced first and thereupon the frequency characteristic in the audio-frequency part is influenced. Thus the cam I4 is at first fully in engagement with the arm H and the coils are in the same axial position opposite each other. The shaft with the cam will now be turned until the arm ll lies directly at the shaft [3. The coupling and hence the band width have reached the lowest value which is retained at further turning. Now, the resistance 9 of the tone control is effectively reduced and owing to the change of the resistance value in accordance with the range F according to Figure 2, a continuation of the control is effected by the cutting off of the high notes in the audio-frequency part.

In place of the variable resistance 9 for the tone control in the audio-frequency part of the receiver apparatus, obviously also a variable condenser can be provided. On the other hand, also a resistor may be employed having a characteristic conforming solely to the range F in Figure 2, and which is temporarily operated by means of a cam or similar element in the manner of the coupling arrangement 4/5, for instance following the termination of the displacement of the coupling arrangement 4/ 5. The cams may be substituted by rods or similarly acting arrangements.

We claim:

1. In signalling apparatus having a high frequency portion and a low frequency portion, means for controlling the band width of the high frequency portion, means for varying the frequency characteristics of the low frequency portion and single operable means adjustable over a predetermined range of movement for controlling both of said first two named means, said first named means being operable by said single means over only a portion of the range of movement of said single means, said second means comprising a variable resistance element operable by said single means over substantially all of the range of movement of the single means, said resistance element being arranged so as to be only slightly effective in the range of operation of said first named means by the single means and producing its maximum eifect in that portion of the range of movement of the single means within which the first named means is not operated thereby.

2. In a modulated carrier signal receiver a carrier frequency portion including a variable band-pass selector, a modulation frequency portion including a variable tone control means, an adjustable controlling means arranged so as to be movable over a predetermined range, means for coupling said selector to said controlling means for adjusting said selector to vary the width of the band of frequencies passed by the selector in accordance with the direction of operation of said controlling means, said coupling means being effective to adjust the selector only over a predetermined portion of the range of movement of said controlling means, means for coupling said tone control means to said controlling means to provide for variably attenuating the higher frequencies passed by said modulation frequency portion in accordance with the operation of said controlling means, said'last named coupling being eifective to provide adjustment of said tone control means substantially throughout all of the range of movement of the controlling means, said tone control means being arranged so as to be only slightly effective in the range of operation of the band-pass selector by said controlling means and producing its maximum effect in that portion of the range of movement of said controlling means within which the selector is not operated.

3. The method of controlling the overall fidelity of a modulated carrier signal receiver having a carrier frequency portion and a modulation frequency portion which comprises first ad- .iusting the fidelity characteristic of the carrier frequency portion from maximum to minimum within predetermined limits and at the same time adjusting the fidelity characteristic of the modulation frequency portion from maximum to a value slightly less than maximum and thereafter adjusting the fidelity characteristic of the modulation frequency portion only from said value slightly less than maximum to minimum within predetermined limits and vice versa.

ALFRED serious. EUGEN S'I'EF'FENS. 

